What football lessons can be sorted from the applause (first half) and ashes (second half) of the Aztecs’ 31-10 loss Friday at No. 13 Stanford?

What’s the takeaway from a dominant, no-flinch road start as running back Juwan Washington slashed and shouldered his way to triple digits by halftime — while Heisman Trophy contender Bryce Love slogged his way to more carries (10) than yards (7)?

What’s the gut feeling about the team, one game in, after a wide receiver carved up the secondary and scheme like a Thanksgiving Day turducken?

Cue, Rocky Long.

“We played better at the line of scrimmage than I thought we would,” Long said Tuesday. “I thought we’d be a little out-manned on the defensive line by their offensive line and a little out-manned on our offensive line by their defensive line. That was not the case.

“We held our own and sometimes we were (at) better line of scrimmage. But we made way too many mistakes on both sides of the ball. Then we had a little trouble covering one of their receivers.”

Or, a lot of trouble.

JJ Arcega-Whiteside used his 6-foot-3 frame — and the Aztecs’ commitment to run support by defensive backs — to obliterate his career high with 226 yards. Peter, robbed. Paul, paid.

“Let’s don’t forget, one of the reasons we played such good run defense was the run support (the secondary) gave,” Long said. “We asked our DBs to be total football players. If all we asked them to do was cover receivers, we would have covered receivers.

“… But then we’d have watched a guy win the Heisman Trophy in the first week of the season.”

So, what did we learn?

We learned … quarterback Christian Chapman continues to be careful with the football and, ultimately, too careful. The senior holds the lowest interception-to-attempts ratio in program history, but holding onto the ball too long contributed to five sacks with four coming in the tide-changing second half.

We learned … safety Parker Baldwin wants to hit. And hit some more. And hit some more after that. He’s tough-nosed and, against the Cardinal, seemed to constantly be around the ball.

We learned … the lines that were exposed last season against Boise State and Fresno State are better. How much remains to be seen, but a performance like that on the road against a Top 15 team seems as encouraging a sign as any from Week 1.

“I think we dominated the line of scrimmage, most definitely,” said senior defensive end Anthony Luke. “I think we won that battle up front.”

We learned … the Aztecs, vulnerable on the corners last season remain vulnerable on the corners this season.

We learned ... there’s no reason to rule out back-to-back-to-back, 2,000-yard rushers at San Diego State. Washington, following NFL picks D.J. Pumphrey and Rashaad Penny, recorded the most yards ever during a road opener (158) in the Division I era. The junior averaged 6.6 per carry, the most by a feature back against an AP Top 25 team since Ronnie Hillman rambled at an 8.0-yard clip against Air Force in 2010.

“We made some holes,” senior right tackle Ryan Pope said. “It’s never good enough, but the physicality was there.”

We learned … that a Rocky Long-coached team will play like a Rocky Long-coached team. Long said he received plenty of unsolicited email advice about double-coverage and zones to deal with any Arcega-Whiteside types on the schedule.

“There’s a lot of things you could do. And there’s a bunch of them we’re not going to do,” Long said. “You can completely change the structure of your defense and have an ability to make sure you cover receivers. Then they’re going to rush for 500 yards.

“We’re going to play our defense the best way we can play our defense and hope that the defensive backs make more plays than they did last week.”

We learned … these Aztecs can take a punch. There’s zero chance Love and Stanford came into this game sleep-walking. Not after last season, when the Aztecs choked the clock in a 20-17 victory over the then-No. 19 Cardinal. Three of Stanford’s first five possessions resulted in three and out.

We learned … that for a game, Stanford made better halftime adjustments.

We learned … that growing pains in the defensive backfield are far from over. Between the five who started back there, there are two sophomores (Trenton Thompson, Tariq Thompson) and two juniors (Ron Smith, Kyree Woods).

“I’ve said the youngest part of our defense was the secondary and that’s the quickest way to lose a game,” Long said. “Young DBs have to play in live action to get better. They don’t get better in practice. They have to see everybody moving around at a faster pace and they have to react to the ball in a stressful situation.

“Skill-wise, it’s the toughest position to play on defense.”

We learned … that players understand a season like this remains a work in progress. Said Luke: “We have to keep it going all four quarters and not just show up in the first half.” From Pope: “Consistency, for sure, is something that needs to be worked on. And it’s being changed in practice as we speak.”

Most of all, as the home opener against Sacramento State approaches Saturday, we ultimately learned … that they’re learning, too.

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